Alex2006

My fc will misfire very bad when the car is not fully warmed up and hits 3800 rpm and it will also misfire when it is fully warmed up but only when the lights are on or rolling down the windows. Could this be an alternator by chance? Or Is it possible that my secondary injector is bad?

diabolical1

iTrader: (3)

welcome to the board.

what is the voltmeter reading when this is happening?

Alex2006

The voltmeter is dropping when the misfire happens

Alex2006

the alternator and battery are completely fine aswell

diabolical1

iTrader: (3)

what about the battery cables? is the ground cable secured and clean?

Alex2006

yes I cleaned it today aswell and it’s still doing it, the bolts are only dropping some of the times when it misfires, could this be a wiring harness issue?

diabolical1

iTrader: (3)

not to belabor the point, but did you also check the other end of the cable (down by the through-bolt at the tranny)?

1. check the harness at the ECU.
2. check the coils to see if they are loose or if there is any corrosion where it contacts the car.

https://www.rx7club.com/2nd-generati...ssues-1002870/

https://www.rx7club.com/2nd-generati...ground-654459/

https://www.nopistons.com/2nd-gen-f-...ble-etc-45685/

now ... switching gears to other possibilities ...

when did you last tune up the car?

old plugs? has it flooded really badly recently?

Alex2006

never flooded to bad and just put in brand new plugs I’ll check the coils today but I’m doubtful that they are bad

diabolical1

iTrader: (3)

for the record, i don't think the coils are bad, but if the alternator and battery are good, like you said, then you could be chasing a poor ground somewhere.

another idea ... maybe try isolating the misfire. try running it on only the leading ignition and see if it still does it.